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/. H. P. from Ideal Diagram.

625

pressure scale, but multiplied by 144 to obtain pounds per sq. ft.
The gaps between areas and saturation curves show work lost, but
while there is a loss on the side s, there is a gain on side T. A
much greater loss occurs from initial condensation, which is not
here shewn, and the total 'missing quantity7 can only be dis-
covered by some construction such as is given at p. 764.
Also it must be understood that the saturation curves cannot be
exactly followed except where good steam jackets are adopted;
the curve should otherwise be nearer Rankine's adiabatic
pyV = C, which falls slightly below the saturation curve.

Calculation of Work and Horse Power from
Theoretical Indicator Diagram.—It is sometimes con-
venient to make rough preliminary calculations from a simple

/IP----

hyperbolic diagram as in Fig. 625, where various losses at the
corners, caused by release, wire-drawing, cut off, &c., are neglected.
Then             Area of BN^/'

Area of CRN G - # V log* *- - f{ (/' + c) Hoge j
Mean effective pressure /« = {(areas BN -h CKNG) -r- L} — p\>

Then>

Horse Power

(See Appendices I. and III.,
33,000         fp. 111 and 931.)